1. Field of the Invention
The present invention relates to a substrate processing apparatus for performing a desired heat treatment through a diffusion process or a chemical vapor deposition (CVD) process.
2. Description of the Related Art
A vertical thermal diffusion apparatus or a vertical decompression CVD apparatus is configured, for example, to receive a substrate in a heat treatment furnace to form a thin film on a processing substrate, heat an interior of the heat treatment furnace using a predetermined heating means, and in most cases, detect a temperature in the heat treatment furnace using a temperature sensor installed at the heat treatment furnace, and control the temperature based on the result.
For example, Patent Document 1 discloses a semiconductor manufacturing apparatus for controlling a temperature through feedback control, which is always stable even when disturbance accompanied by rapid cooling occurs. The semiconductor manufacturing apparatus performs temperature control by a cascade control loop using a thermocouple (a heater thermocouple) installed around a heater for heating the interior of a heat treatment furnace and a thermocouple (a cascade thermocouple) installed between a heat distribution tube and a reaction tube in the heat treatment furnace when a temperature elevation process is performed or a target temperature is maintained, and performs temperature control by directly switching a control loop using only the cascade thermocouple when a heater temperature is lowered.